Light amount adjusting device, lens barrel, and image capturing apparatus

Patent metadata

Field	Value
Publication number	US-2016259100-A1
Application number	US-201615059092-A
Country	US
Kind code	A1
Filing date	Mar 2, 2016
Priority date	Mar 5, 2015
Publication date	Sep 8, 2016
Grant date	—

Abstract

A light amount adjusting device includes ND filters rotating around shafts serving as rotation shafts and moving between in-use positions and retracted positions, arranged on a base plate. The respective ND filters include uniform density portions, gradation portions, and transparent portions. If the ND filters are in the retracted positions, the transparent portions of the respective ND filters overlap in an area facing an aperture to cover the entire aperture with the transparent portions. If the ND filters are in the in-use positions, the gradation portions of the respective ND filters overlap in an area facing the aperture to cover the entire aperture with the gradation portions and the uniform density portions. Moreover, a combined density acquired when the gradation portions overlap in just proportion is substantially the same as an optical density of each of the uniform density portions.

First claim

What is claimed is:

1 . A light amount adjusting device that adjusts an amount of light passing through an aperture, the light amount adjusting device comprising:
a first filter, including a transparent area and a non-transparent area, configured to move between a retracted position and an in-use position in an area including an area facing the aperture; and a second filter, including a transparent area and non-transparent area, configured to move between a retracted position and an in-use position in an area including the area facing the aperture, wherein, if the first filter and the second filter are in the retracted positions, the transparent area of the first filter and the transparent area of the second filter overlap in a position facing an entire area of the aperture, and wherein, if the first filter and the second filter are in the in-use positions, the transparent area of the first filter and the non-transparent area of the second filter overlap in a position facing the aperture, and the non-transparent area of the first filter and the transparent area of the second filter overlap in a position facing the aperture.

2 . The light amount adjusting device according to claim 1 , wherein the non-transparent area is an area in which an optical density is substantially uniform.

3 . The light amount adjusting device according to claim 1 , wherein the non-transparent area includes a uniform density area in which an optical density is substantially uniform, and a gradation area that is arranged between the transparent area and the uniform density area and includes an area in which an optical density continuously changes from the transparent area to the uniform density area, and
wherein, if the first filter and the second filter are in the in-use positions, the transparent area of the first filter and the uniform density area of the second filter overlap in a position facing the aperture, the uniform density area of the first filter and the transparent area of the second filter overlap in a position facing the aperture, and the gradation area of the first filter and the gradation area of the second filter overlap in a position facing the aperture.

4 . The light amount adjusting device according to claim 3 , further comprising:
a base plate including the aperture; a portion configured to define the in-use position of the first filter and the in-use position of the second filter; and a portion configured to define the retracted position of the first filter and the retracted position of the second filter, wherein the base plate includes: a shaft to which the first filter is rotatably attached; and a shaft to which the second filter is rotatably attached, and wherein a relational expression of 0.1<δ×α×2×d<0.6 is established, where δ [mm] is a position error in the portion which defines the in-use position of the first filter and the in-use position of the second filter, a is a ratio of a distance between the shaft and the portion which defines the in-use position of the first filter and the in-use position of the second filter to a distance between the shaft and an optical axis center, and d is a density change rate [/mm] that is an amount of changes in optical density per 1 [mm] in the gradation area.

5 . The light amount adjusting device according to claim 4 , wherein a relational expression of 0.5/α<d<3/α is established.

6 . The light amount adjusting device according to claim 4 , further comprising an actuator configured to rotate the first filter and the second filter,
wherein the base plate further includes a hole for rotation of the first filter and the second filter, wherein the first filter further includes a hole that is arranged facing the hole formed in the base plate, wherein the second filter further includes a hole that is arranged facing the hole formed in the base plate, wherein the actuator includes a rod member to be inserted into the holes formed in the first filter, the second filter, and the base plate, and moves the rod member to rotate the first filter and the second filter, and wherein the portion which defines the in-use position of the first filter and the in-use position of the second filter and the portion which defines the retracted position of the first filter and the retracted position of the second filter are a portion in which the rod member contacts the hole formed in the base plate.

7 . The light amount adjusting device according to claim 1 , wherein, if the first filter and the second filter are in the in-use positions, a value acquired by combining optical densities of the first filter and the second filter which overlap in the position facing the aperture is substantially uniform.

8 . A lens barrel comprising the light amount adjusting device of claim 1 .

9 . An image capturing apparatus comprising:
the lens barrel of claim of 8 ; and an image capturing element.

Assignees

• Canon Kk

Inventors

• Uehara Takumi

Classifications

• H04N23/55

  Optical parts specially adapted for electronic image sensors; Mounting thereof · CPC title

• H04N23/75

  by influencing optical camera components · CPC title

• G02B5/205 Primary

  Neutral density filters · CPC title

• G02B7/006

  Filter holders · CPC title

• G03B9/02

  Diaphragms · CPC title